Insulated die set



Feb. 23, 1965 H. H. COFFIN msuwrzo on: ssrr Filed Nov. 17, 1960 FIG.I

FIG.2

INVENTOR.

HARLAND H. COFFIN FIG.3

United StatesPatent Oflice 3,170,735 INSULATED DIE SET Harland H. Collin, Bridgeport, Conn, assignor to Producto Machine Company, Bridgeport, Conn., a corporation of Connecticut Filed Nov. 17, 1960, Ser. No. 69,891

2 Claims. (Cl. 308-4) deviation, which is an essential requirement in the process.

The production of dies with such apparatus requires the use of an electrode in the form ofthe cavity of the die to be produced that is usually fixed to the upper plate of the die set. The material from whichthe die is to be made is fixed to the lower plate of the die set. Since the process involves electronic apparatus capable'of producing a voltage having between75,000 to 300,000 cycles per second, the lower plate must be insulated from the upper plate.

Many attempts have been made in an effort to insulate these plates from each other with little practical success because a serious problem arises in maintaining the necessary accuracy between the guide pins and guidesleeves of the die set.

The principal object of the invention is to produce a die set having the upper plate insulated from the lower plate without detracting from the inherent accuracy of the die set. 7

Another object of the invention is to produce such a die set in which the insulating construction thereof does not prevent the die setfro'm being used in punch press production runs.

Still another object of the invention is to produce such a die set inwhich theguide pin is insulated from the bottom plate. 7

Still another object of the invention is to produce such a die set in which the insulated pin construction can be used with existing as well as special die sets without alteration.

Another obejct of the invention is to provide such a die set in which any guide bushing may, be employed.

A still further object of the invention is to provide such a die set in which the insulatedgpin construction rammed Feb. 23; 1965 The above, other objects and novel features of the inven tion will become apparent from the following specification and accompanying drawing which is merely exemplary. I

In the drawing:

FIG. 1 is a top plan view of a die set to which the principles of the invention have been applied;

FIG. 2 is an elevational view of the die set shown in FIG. 1; and I FIG. .3 is a sectional view taken substantially along line 3,3 of FIG. 2.

Referring to the drawing, the principles of the invention are shown as applied to a die set including a bottom plate 10 having slots 11 and 12 for receiving fastening meansadapted rigidly to hold the bottom plate 10 to a supporting structure. Two or more case-hardened studs 13 and 14 may be rigidly held intthe plate 10 in parallel relation by a press fit within bores in plate 10.

An upper plate 15 may be provided with a stud 16 for engagement with a head member of the electrical discharge-machining equipment that is adapted to be fed downwardly toward the bottom plate 10 at a predetermined 'feed rate. The upper plate 15 may include two or I more bores 17 and 18 equal to the number of studs 13 and 14 and spaced so as to register therewith. Each bore 17 and 18 is adapted to have pressed therein a casehardened sleeve 19 for guiding the upper plate 15 and for maintaining itparallel with bottom plate 10 at all times during its feeding movement.

The upper plate 15 may have fixed to its under surface an electrode in the form of the internal cavity of a die to be formed, and material from which the die is to be made may be fixed to the bottom plate 10. As the plate 15 is fed downwardly, alternating voltage of between 75,000 and 300,000 cycles per second is provided across necessitates insulating plate 10 from plate 15.

In another aspect of the invention, a thin layer of bonding material such as molten molybdenum may be sprayed onto thereduced diameter portion.

In still another aspect of the invention, the end of the pin containing the bonding material may be coated with a ceramic material such as aluminum oxide, aluminum oxide and titanium oxide, or zirconium oxide. 7 4

In still another aspect of the invention, the ceramic coated end" of the guide pin may; then be surrounded by I jceramic end may then. be turned to a diameterwhich will make a press fit upon the end being insertedwithin a bore 'of'a bottom plateof'a die set.

Referring to. FIG. 3, this has been accomplished by reducing the diameter of pin 13 to a diameter 20. A thin layer 21 of bonding material may be applied 'to. the reduced diameter portion of pin 13. This bonding material may be pure molybdenum. It may beapplied by feeding a strip of the metal through an acetylene flame at the end of a spray gun in such fashion that molten metal is sprayed onto the reduced diameter portion of pin 13. r

A ceramic coating 22 may then be applied to the bonding' metal, and it may comprise aluminum oxide, aluminum oxide mixed with titanium oxide, or zinconium oxide. The ceramic oxide may be fed through an acetylene flame at the end of a spray gun which causes it to melt and be thrown on top of the bonding layer on the; surface of the pin .13. It. has been found that a sufficient thickness, of ceramic should be applied to withstand a breakdown voltage of about 700 volts, thereby providing an .adequate safety factor in the operation of electrical discharge machining apparatus.

'A layer of metal such as pure molybdenum; l8-8 I or type 316 stainless steel maysurround the ceramic layer; This metalmay also be sprayed onto the ceramic coated end by feeding a stripof the metal into an acetylene flame at the end of aspray gun. Although the metal sleeve 23 has been described as having been sprayed on, such being the. preferred method, it could, ofcourse,

be cast or'fotherwise formed and be applied by shrinking diameter and finally pressed into a bore 24 of the bottom plate 10 in the usual way such pins normally are mounted in the bottom plate of a die set.

While a preferredembodiment has been disclosed, it

is evident thatthe bore 24 could be lined with bonding and which latter is subsequently coated with sprayed metal. The bore could then be reamed and the pin 13 pressed thereinto.

From the foregoing it is evident that a die set has been provided having guide pins that are insulated from the bottom plate and whichare held by a press fit in bores within the bottom plate. Furthermorqit is evident that the metal sleeve surrounding the ceramic insulating layer maintains the insulation intact during the pressing of the pin into the bore within the bottom plate.

Although the principles of the invention have been shown and described in detail to fully disclose one embodiment of the invention, it will be evident that changes may be made in such details and certain featuers may be used without others without departing from the principles of the invention.

What is claimed is:

1. In a die set, a bottom plate; a top plate; guide pin means having two ends, one of which is mounted within a bore in one of said plates; guide bushings attached to the other of said plates in position to register with said guide pin means; a layer of bonding material on the one end of said guide pin means; a layer of a ceramic oxide integrally attached to said guide pin means by said bonding material; and a layer of metal surrounding said layer of ceramic oxide, said layer of metal and said bore 4 having precise diameters forming therebetween a metalto-metal press fit.

v 2. In a die set, a botom plate having a wall surface forming an opening therein; a top plate having a wall surface forming an opening therein; guide post means having a surface mounted in the opening in one of said plates; bushing means mounted in the opening of the other of said plates slidingly receiving said guide post means; a layer of bonding material on one of said surfaces; a ceramic oxide layer integrally united to said one of said surfaces by said bonding material; and a layer of metal integrally attached to said ceramic oxide, the dimension of said layer of metal being such as to form a metal-to-metal press fit within one of said openings.

References Cited in the file of this patent UNITED STATES PATENTS 1,126,975 Furber Feb. 2, 1915 1,157,666 Bennett Oct. 26, 1915 1,902,955 Holmes Mar. 28, 1933 2,238,302 Baumbach Apr. 15, 1941 2,272,210 King Feb. 10, 1942 2,356,387 Danneman Aug. 22, 1944 2,631,222 Niebling Mar. 10, 1953 2,636,254 Gunning Apr. 28, 1953 2,749,987 Janiszewski June 12, 1956 2,917,140 Omley Dec. 15,1959 3,042,744 Shoor July 3, 1962 

2. IN A DIE SET, A BOTOM PLATE HAVING A WALL SURFACE FORMING AN OPENING THEREIN; A TOP PLATE HAVING A WALL SURFACE FORMING AN OPENING THEREIN; GUIDE POST MEANS HAVING A SURFACE MOUNTED IN THE OPENING IN ONE OF SAID PLATES; BUSHING MEANS MOUNTED IN THE OPENING OF THE OTHER OF SAID PLATES SLIDINGLY RECEIVING SAID GUIDE POST MEANS; A LAYER OF BONDING MATERIAL ON ONE OF SAID SURFACES; A CERAMIC OXIDE LAYER INTEGRALLY UNITED TO SAID ONE OF SAID SURFACES BY SAID BONDING MATERIAL; AND A LAYER OF METAL INTEGRALLY ATTACHED TO SAID CERAMIC OXIDE, THE DIMENSION OF SAID LAYER OF METAL BEING SUCH AS TO FORM A METAL-TO-METAL PRESS FIT WITHIN ONE OF SAID OPENINGS, 